Piston



July 14, 1942.

o. c. PILLAR PISTON Filed Oct. 22, 1941 2 Sheets-Sheet l INVENTOR 0507/? 67PM. L HR.

' July 14, 1942. 4 o. c. PILLAR 2,289,994

PISTON Filed Oct. 22, 1941 2 Sheets-Sheet 2 BY Tom INVENTOR PatentedJuly 14, 1942 PISTON Oscar 0. Pillar, Philadelphia,

one-half to Ringless Piston mington, Del., a corporation Pa.,' assignorof Corporation, Wilof Delaware Application October 22, 1941, Serial No.416,113

8 Claims.

Some of the objects of the present invention are to provide .an improvedpiston for use in reciprocating engines, pumps, and the like; to providea piston wherein provision is made for adequate sealing against loss ofcompression and oil pumping; to provide a piston which eliminates pistonslack and slap; to provide a piston which reduces wear to a minimum bydistributing the points of wear substantially uniformly about thecircumference of the encompassing cylinder; to provide a piston having aplurality of expansible bands so arranged with respect to each otherthat in action one band compensates for any undesirable action ofanother; to provide a piston wherein two expansible bands are soassociated in position upon the piston body that the major pressure ofone is exerted over an area which is not subjected to the major pressureof another band; to provide a piston wherein any points exposed to oilare automatically sealed to prevent leakage; and to provide otherimprovements as will hereinafter appear.

This application is a refiling of forfeited application Serial No.157,503, filed August 5, 1937, with additional modification.

In the accompanying drawings Fig. 1 represents an elevation of one sideof a piston embodying one form of the present invention; Fig. 2represents anelevation of the side of the piston opposite to that shownin Fig. 1; Fig. 3 represents a bottom plan; Fig. 4 represents anenlarged section on line 4-4 of Fig. 1; Fig. 5 represents a top plan;Fig. 6 represents a side elevation in part section of a modified formof. the invention; Fig. '7 represents a plan of one of the piston bands;Fig. 8 represents a side elevation of one band; Fig. 9 represents asection on line 9-9 of Fig. 8; and Fig. 10 represents a side elevationof the second band.

Referring to the drawings one form of the present invention consists ofa piston body In of hollow cylindrical construction having ahead IIformed integral therewith as well as the usual diametrically disposedbosses I2 for receiving the customary wrist pins by which the piston isattached to the crank. As here shown the body I!) is provided with twocircumferential grooves I3 and I4, the former I3 being parallel to andin close proximity to the head II, while the latter I4 opens into theformer I3. The two grooves I3 and I4 are so dimensioned and located asto form the major portion of the length of the piston body. The grooveI3 which is adjacent to the head II is preferably of greater depth thanthe groove I4 and consequently forms a circumferential ledge or land I5which serves as a support for a resilient metal split band I 6 mountedin the groove I3. In finished and assembled condition one end of theband I6 is rigidly fastened to the piston body III while the lengththereof brings the free end around into spaced juxtaposed relation tothe aforesaid fixed end as indicated by the space H. Normally the bandI6 tends to expand eccentric to the piston head I I but when assembledin a cylinder the space I? allows the band I6 to contract the requiredamount. In the present instance the end of the band I6 which is to befixed is secured by suitable pins or rivets I 8, though where the metalused permits it may be secured by welding. In connection with themounting of the band It it should be noted that while its upper andlower edges have a snug fit against the respective parts of the bodyII], the rear wall, however, forms a clearance 20 with the body which inoperation becomes filled with oil and thus servesto prevent loss due toleakage past the joints.

The groove I4 serves to receive a split band 2| of resilient material,one end being made fast to the body III by a pin or rivet 22, or bywelding, if found desirable. Since the groove I4 lies in the same planeas the bosses I2 the band 2I is so located that opposed ends meet incoaxial relation to one of the bosses I2. Hence for purpose of wrist pinassembly the aforesaid band ends are substantially semi-circular incontour, being subscribed on a diameter not less than the diameter ofthe bore of the boss I 2. Thus with the band 2| retracted to itsmaximum, full unrestricted access can be had to one of the bosses I2. Inassembled condition the upper face of the band 2I rides against thelower face of the band I6 to form an effective seal between the twobands. The rear face of the band 2| normally leaves a clearance 23 whichfills with oil to function in eifect as a packing to prevent leakage.The lower face of the band 2I is bevelled to form a relatively sharpexterior circumferential edge 24 which serves "as an oil scraper forremoving excess oil and directing it downward to find escape throughports 25 traversing the annular flange 26 forming the bottom end of thebody III. In this connection it should be noted that this flange 26 isbevelled to form a relatively sharp, outwardly flared edge 21 which actsin the capacity of an oil scraper. Preferably the ports 25 extenddiagonally downward through the flange 26 and have inlets located in acircumferential groove 28 which serves to collect oil in the manner ofthe customary oil ring used in pistons of ordinary construction.

By reference to Fig. 4 it will be seen that the point of maximumeccentricity of the band I6 is at one side of the piston body I whilethe point of maximum eccentricity of the band 2| is at the opposite sideof the piston body l0. That is to say when considered with respect tothe axis of the piston the split in one band is angularly disposed with'respect to the split in the other band. While a relatively wide range ofangular relation is possible with results improved over ordinary ringpistons, the preferred angle is approximately one hundred and eightydegrees. Each band It and 2! is preferably provided with oil grooves 35in the outer circumferential face thereof.

In operation the piston of the present invention, in so far as itrelates to wear, pumping, loss of compression, etc., functions quitedifferently from the ordinary piston equipped with the usual successionof freely movable expansible rings. In such prior constructions themaximum expansion effort of the ring is exerted at approximately twodiametrically opposite points so that uneven wear occurs in the cylinderwhich results in the well known egg shaped cylinder and its inefficientoperation. The expansion of the bandsof the invention takes place in anew and novel way in that each expands outwardly using the fixed endmore or less in the manner of a fulcrum. To express the action inanother way it may be said that the expansion takes placecircumferentially of the body of the piston quite in the way of a brakeband wrapping itself about a drum. Hence wear instead of beingconcentrated at two distinct points is distributed uniformly about thewhole adjacent area of the piston. Having this action in mind for one ofthe bands it is obvious since the other band has a substantiallycomplemental position that any tendency to Wear at one place iscompletely compensated by a like wear at another place so that the truecylindrical contour of the cylinder is maintained.

It should also be noted since the expansible bands occupy substantiallythe full length of the piston body the piston is under perfect controlthroughout its length and whether or not a skirt is provided as a partof the piston there can be no piston slack or slap. In the preferredembodiment of the invention a skirt is not believed to be necessary.

In the form of the invention shown in Figs. 6 to 10 inclusive, the bodyIll is provided with a circumferential groove 3|, the upper boundingface 32 of which is a plane surface at right angles to the axis of thebody l0, and the lower bounding wall 33 of which is a plane surfaceangularly disposed to the axis of the body ID. This angularity is suchas to converge upwardly from its junction with the rear wall of thegroove 3| towards the upper face 32. Preferably this angle is about tendegrees to the horizontal.

For sealing purposes, two split bands 34 and 35 are received within thegroove 3| in superposed abutting relation, and having a combined widthsuch that the top of ring 34 seats against the face 32 while the bottomof ring 35 seats against the wall 33.

In order that the band 34 can automatically adjust itself to compensatefor wear and maintain a leak-proof joint between the faces 3i and 32,the upper face 36 of the band 35 is bevelled outwardly and downwardlywhile the lower face 31 is bevelled outwardly and upwardly so thattogether the converging faces become a wedge. Thus, in assembledcondition, the face 35 rides against the complemental bevelled face 38on the bottom of the band 34, and the face 31 rides against thecomplemental bevelled wall 33 of the groove 31. In this connection itshould be noted that the ring 34 is a free ring, that is, it is notfastened to th piston body i0, though the ring 35 is pinned near one endby a pin 40 to the body ll]. Thus the ring 35 maintains the wrap aroundgripping action heretofore described and is freely expandible to act asa Wedge by reason of the bevelled engaging faces. Hence as wear developsthe ring 35 automatically compensates for it by radial expansion, butleakage is prevented because this relative change only forces the ringsmore tightly against all joint surfaces.

Having thus described my invention, I claim:

1. A piston consisting of a head, an annular body part including wristpin bosses and two circumferential grooves, one of said groovesencircling said bosses, split resilient bands located respectively insaid grooves, the band in the boss encircling groove having its meetingends at opposite sides respectively of one of said bosses, and separatemeans for securing one end of each band to said body part.

2. A piston consisting of a head, an annular body part including wristpin bosses and two circumferential grooves, one of said groovesencircling said bosses, split resilient bands located respectively insaid grooves, the band in the boss encircling groove having its meetingends at opposite sides respectively of one of said bosses, and separatmeans for securing one end of each band to said body part, the twosecuring means being circumferentially out of alinement.

3. A piston consisting of a head, an annular body part including wristpin bosses and two circumferential grooves, one of said grooves beingdeeper than the other, split resilient bands located respectively insaid grooves and both in assembled condition expanding against the innerface of a cylinder, separate means for securing one end of each band tosaid body part, and

means including an offset ledge to prevent leakage past the joints ofsaid bands with said body.

4. A piston consisting of a head and an annular body part, means forattaching said piston to a connecting rod, said body part having acircumferential groove Of a width approximately equal to the length ofsaid body part, one circumferential portion of said groove being deeperthan the other portion to form a circumferential ledge between saidportions, two split resilient bands fitted respectively into saidportions to form a spring urged wall to abut the encircling wall of thepiston cylinder with one of said bands riding in contact with the otherband and with said ledge to restrict oil leakage, and separate meanssecuring one end of each band to said body part, said means beingarranged at opposite sides of said body part with respect to each other.

5. A piston consisting of a head and an annular body part, said bodypart having a circumferential groove, two split resilient bands arrangededge to edge and dimensioned to fit snugly within said groove, and meansto press one band against the other under radial expansion of saidbands, said means, including two outwardly converging bevels, one bevelbeing between said body part and one ring, and the other bevel beingbetween the two rings, whereby oil leakage between said bands and bodypart is pre- Vented.

6. A piston consisting of a head and an annular body part, said bodypart having a circumferential groove, one wall of said groove having abevelled face, a split band bevelled on one edge complementally to saidbevelled face and contacting therewith when said band is assembled insaid groove, said band having its opposit edge provided with a bevel, asecond split band fitting the remaining space in said groove and havinga bevelled face seating on the second bevelled edge of said first band.

'7. A piston consisting of a head and an annular body part, said bodypart having a circumferential groove formed with upper and loweroutwardly convergent surfaces, two split rings fitting said groove inmutually edge to edge rel-ation, said edges being complementallybevelled and coacting to cause the expansion of one ring to supplementthe expansion of the other ring while simultaneously initiating pressureaxially of said piston to seal the ring groove joints.

8. In pistons, a body part having a groove, a split resilient ring insaid groove, means to rigidly fasten one end of said ring to said bodypart for progressive circumferential expansion, and a second ring insaid groove coacting with said first ring and free to expand radiallythroughout its length, said rings having overlapping complementallybevelled surfaces.

OSCAR C. PILLAR.

